In electrically driven windscreen wipers, the wiper arms are driven via a reduction gear by the shaft of an electric motor. Here, it is important that the position of the angle of rotation of the reduction gear wheel in the gear housing is assigned to a certain angular position of the windscreen wiper. For this reason, during the mounting of known drives, the gear wheel driving the wiper arm is moved into a certain angular position (parked position) and subsequently, the wiper arm located in the corresponding angular position is locked into position opposite the gear wheel. This takes place because on the output shaft of the gear wheel located in the parked position, the crank lever is placed in a defined angular position and is locked into position opposite the drive shaft. At that point, it is assumed that the rotation of the gear wheel, which is in the same direction, is converted via the crank lever into a pivoting movement of the wiper arm. The above means, however, is also appropriate when the pivoting movement of the wiper arms is achieved by reversing the direction of rotation of the motor. Here, according to its nature, the crank lever may be omitted and possibly the wiper arm itself or a drive member of a simple linkage arrangement can be placed on the drive shaft of the gear wheel in a defined angular position.
The known way of fixing the crank lever with respect to the drive shaft can be seen, for example, in DE-OS 44 02 476. This mode of attachment is disadvantageous because the drive shaft must be provided at its end with a conical fluting to which a threading connects. Furthermore, an assigned fluting is required in connection with the crank lever and finally, a nut which can brace and stop the crank lever with respect to the drive shaft.
The known assembly method is costly with respect to the required parts and the required assembly time. Moreover, the known construction requires more room than absolutely necessary since the end of the crank lever which is turned away from the output shaft must be located outside the plane of the attachment nut. Thus, it is necessary for the crank lever to bend outwards beyond the outer front face of the nut.
It is the task of the invention to indicate a new method for assembling the drive shaft at the gear wheel, whereby the mentioned disadvantages are prevented. The invention consists in principle of a gear wheel which is moved independently of the output shaft, into a predetermined angular position (parked position) and an output shaft, which is in defined angular position, is then connected to the gear wheel. The described mode of connection is advantageous not only for drive mechanisms of windscreen wipers, but rather for every case when the drive shaft, located in a predetermined angular position, is to be tightly connected to the gear wheel which is in a certain angular position, as may be the case, for example, with crankshafts and similar arrangements.
In essence, the advantage of the invention consists in that the output shaft and the angle lever (or crank lever) may already be rigidly connected to each other prior to installation. This can be achieved, for example, by riveting, welding, caulking or also by means of a single-piece cast part. Thereby, the above-described connection parts, such as threadings, nut, fluting and the like are omitted.
A particularly advantageous connection between the drive shaft and the gear wheel can be achieved by the combination of features of the invention. However, other connection types are also possible. For example, by means of an appropriate longitudinal fluting of the drive shaft and an appropriate bore hole in the gear wheel, an appropriate synchronization force of the gear wheel with respect to the drive shaft can be provided without requiring the two mentioned drive elements to be pressed against each other.
A refinement of the invention provides an appropriate support for the gear wheel with respect to the drive shaft. For example, this can take place either directly, wherein a suitable support device forms an abutment for the gear wheel during the pressing process or even indirectly, wherein the gear wheel supports itself against the adjacent housing wall in its longitudinal direction and the support area of the housing is in turn supported from the outside by means of a holding device during the pressing process.
The method of the invention assumes that at the beginning of the mounting process, the gear wheel is moved into the defined end position (parked position), wherein the corresponding rotation is still independent of the rotary position of the drive shaft. During this initial rotation, the gear wheel should be mounted so that it can rotate. Within the framework of the invention, it is conceivable to provide an auxiliary shaft for this purpose instead of the drive shaft or to push the drive shaft only far enough into the bearing hole of the gear wheel, so that the gear wheel can rotate about the drive shaft while, nonetheless, being secured in radial position. For the final locking into position of the gear wheel with respect to the output shaft, either the auxiliary shaft is removed and then the output shaft is press-fitted or the output shaft, in a second case, is tightly connected to the gear wheel by means of a pressing force.
One combination of features of the invention proposes an electrical windscreen wiper drive mechanism which is particularly suited for the purpose of carrying out the process and, especially, for an initial rotation of the gear wheel into its final position, when the output shaft is removed. The mounting of the gear wheel is particularly simple due to the application of a combination of features in which projections are provided which extend parallel to the longitudinal axis of the gear wheel and which engage a rotating cover surface of the gear wheel and thus secure the gear wheel in the radial direction. Preferably, the securing of the gear wheel in the axial direction takes place by means of assigned side walls of the gear housing which engage the appropriate front faces of the gear wheel itself or a hub of the gear wheel. Since the gear wheels are frequently provided with a toothing along the outer periphery, in a refinement of the invention, a combination of features includes a gear wheel which has an essentially cylindrical hub that protrudes along its longitudinal axis, wherein the cover surface of the hub can engage the mentioned projections. Naturally, also two hubs may be provided which connect to the two lateral surfaces of the gear wheel.